Shot-firing system



March so 192s. 1,578,998

J. J. JAKOSKY SHOT FIRING SYSTEM Filed March '7 1925 F'IELI.

Fll3'-Z.

/7 m W Q W/TNESSES UNITED J'OHN'J. JAKOSKY, or PITTSBURGH. PENNSYLVANIA,Assrenon or ONE-THIRD T0 7 PATENT. OFFIC.

EDWARD STEIDLE, OF PITTSBURGH, PENNSYLVANIA.

SHOT-FIRING SYSTEM.

Application filed March 7, 1925.' Serial No. 13,745;

To all whom it may concern:

Be it known that 1, JOHN J. JAKOSKY, a citizen of the United States, anda resident of Pittsburgh, in the county of Allegheny and State ofPennsylvania, have invented a new and useful Improvement in Shot-FiringSystems, of which the following is a specification.

. The invention relates to shot firing, by which is meant thedetonating, igniting or exploding of charges of detonative or explosivematerial used for blasting in coal andmetal mines, open pit mining, rockexcavations, stone quarries, etc.

In the customary practice of firing shots, a detonator having short leadwires connected to it is properly positioned in a charge, and its leadwires are electrically connected to lead conductors which are ofsuflicient are electrically connected to a shot firing apparatus, whichusually comprises a blasting machine, power circuit or battery, and a iswitch for closing a circuit through one or the other and the long leadconductors. When the switch is closed, adirect of alternating currentflows through the conductors to fire or prime the detonator.

In the use of this apparatus, premature blasts occasionally occurresulting in serious, and sometimes fatal, accidents to workmen. It hasbeen found that such premature blasts are due largely to various strayand leakage currents that gain access to the long lead conductors, whichfrequently have faulty or insuflicient insulation at splices, and atother places where the insulation is abraded or otherwise injured. Theconditions of serv ice are such that, from a practical point of view. itis impossible to assure adequate insulation throughout the entire lengthof the lead conductors.

The currents which may gain access to these conductors and causepremature firing of shots are either alternating currents of frequenciesthe same as those of commercial power or supply lines. or are directcurrents.

For example, if insufiicicntly insulated portions of the long leadconductors happen to' 'contact with electric track rails, or signalmines and quarries makes favorable conditions for the conduction ofstray currents from grounded conductors or from leakage points ofsupposedly insulated conductors. I have found from extensive experimentsthat the resistanceof different earth strata maybe such as toafford veryfavorable conditions for the development of high potentials betweentwo'exposed or insufficiently insulated portions of the long leadconductors used in shot firing apparatus, and when leakage currents arepresent in such strata there are afforded extensiveareas for suchcurrents to gain access to the long lead conductors and cause prematurefiring.

A further characteristic of shot firing apparatus of the characterexplained is that the long lead conductors must be quite large in orderto carry the relatively low voltage and high amperage currents generatedby a battery or blasting machine, and because of this there is so muchresistance to the flow of current and so much loss of voltage at splicesandjoints that not infrequently there is not sufficient electroinotiveforce available to send a current of sufficient magnitude to fire a shotwhen the circuit is closed through the battery or blasting machine.

The object of this invention is to provide an economic shot firingsystem whereby such stray and leakage currents as may be found in theconditions of service cannot under any'circumstances effect a prematureblast, and in which the prejudicial effect of loss of shot firingcurrents is eliminated.

The shot. firing system provided accordii-i'g to this inventioncomprises two essential elements, first, a generator for generatorder tohave premature firing take place, because the dampness which prevails'in' at least to any iug an alternating current of high voltage and lowamperage, and of a frequency much greater than that of commercialcurrents, and second, a transformer for transforn'iing the current sogenerated into one of low voltage and highamperage fur firing ashot orshots, the generator and transformer being connected by long leadconductors so that the former may be placed at a safe distance from acharge to be fired, and the latter placed close tothe charge.

The transformer, to the secondary of which the short lead wires of oneor more detonators may be attached, is so designed or tuned that it iscapable of transforming substantial extent, only currents of the highfrequency generated by the generator element of the system. Be causedirect current passing through the primary of a transformer will notinduce any current in its secondary, no direct cur-- rent which may gainaccess to the long lead conductors will have any effect upon a detonatorin circuit with the secondary. Furthermore, because the transformer istuned to transform onlycurrentsof a much higher frequency than those ofcommercial alternating currents, any alternating current which, underthe conditions of service, may gain access to the long lead conductors,will not be of such frequency as to cause the transformer to inducesufiicie'nt current in its secondar to prime orfire a detonator.Therefore, t eshot-firing effect of stray currents is entirelyeliminated, and a shot may be fired only by the very highfrequencycurrent generated by the generator element of the system, and to whichthe transformer is tuned.

The invention is illustrated inthe accompanying drawings of which Fig. 1is a wiring diagram of the preferred system; Fig. 2 a wiring diagram ofa "modification; and Fig. 3 a perspective bodying the system.

In the embodiment of theinvention illustrated in Fig. 1, the generatorelement of the system comprises a battery 1, which may consist of aplurality ofdryo'r storage battery cells, a battery circuit 2 3, a.-transformer having a primary 4 and a. secondary 5, and a circuitinterrupterfor causinga rapidly pulsating current to flow through thebattery circuit and primary of the'transformer which forms apart of-suchcircuit. The circuit interrupter may comprise a leaf spring 6 ofconducting material electrically supported at one end and connected by awire 7 to the battery circuit. At its free end spring 6 is provided withan armature 1 1 which is attracted by the magnetic flux threading core12 when current flows in primary 4, and with a contactor 8 adapted tomake and break contact with a contact element which may take the form ofan adview of apparatus em just-able Set screw 5) mounted in an arm 10 ofconducting n'iatcrial, which armis separated from spring 6 by a body ofinsulation 11. Ina manner well known inthe art, the armature 14 andcontact element 8 vibrates between the end of the transformer core 12and contactor 9 causing a pulsating nating current being of the samefrequency.

as the rate of interruption of the direct current. The high voltage lowamperage alternating current thus generated may be of differentfrequencies providing its frequency is much higher than that ofcommercial currents. By way of example, and not of limitation, theinduced alternating current may have a frequency of 500.

The current thus generated is conducted through long lead conductors 15to the primary 16 of a transformer which forms the second element of thesystem, and which, as

already stated, is tuned to transform only currents of the same,'orsubstantially the same, frequency as that generated by the generator.The secondary'17 of the transformer is provided with. suitable contactterminals 18 for making electrical connection to the small wiresattached to shot priming detonators.

To avoid injury to the secondary 5 of the generator and to the primary16 of the transformer by stray currents which may leak into the longlead conductors 15, protecting devices such as fuses 19 and 20 may beplaced in the circuit adjacent to these elements, as is clearlyindicated.

Instead of using a generator of the type explained with reference toFig. 1, a high frequency alternating current having {a high voltage andlow amperage may be generated by a magneto or alternating currentgenerator 21, as illustrated in Fig. 2,

the magneto being adapted to be operated manually in any desired or wellknown manner. When a magneto is thus used, its armature brushes may bedirectly connected to. the long lead conductors 15, the transformerelement of the system, the primary of which is connected to the otherend of these conductors, may be the same as that explained withreference to Fig. 1. In place of the fuses 19 and 20 of Fig. 1, blockingcondensers 31 and .32 may be placed in the circuit adjacent to themagneto 21 and primary 16 to protect them against becoming burned out byleakage currents which may gain access to the long lead conductors 15.

As generally illustrated in Fig. 3, the entire generator element may behoused in a small casing 25 which may be readily transferrcd from placeto place, and the transforiner element may likewise be housed in a smallcasing 36 which may be placed near a charge to be tired, the generatorbeing electrically connected to the primary of the transformer by thelong lead conductors 15, and the terminals 18 of the secondary of thetransformer being connected to short lead wires 27 of a detonator 28. Toprevent thesecondurtors from becoming injured by falling coal or rock,they may be protected adjacent the transformer by a suitable magneto 21.

sheath 26 of metal or other material, to which there may be attached ahandle 33 for withdrawing casing 36 from beneath blasted coal or rock,

Briefly reviewing the operation of the systern, and having referencefirst to the embodiment of the invention illustrated in Fig. 1, arapidly pulsating current may be caused to flow through the batterycircuit by closing switches 30 in conductors 2, 3, which current inducesa high voltage low amperage current in the secondary 5 of thetransformer of the current generator element. This current is in turntransformed by the transformer element 16, 17, into a low voltage highamperage current suitable for priming a detonator. In the embodiment ofthe invention illustrated in Fig. 2, the high voltage low amperagecurrent may be directly generated by suitably operating the Because, forthe reasons explained, commercial stray or leakage currents which maygain access to the long lead conductors 15 cannot set up adetonatorpriming current in the secondary 17 of the transformer elementof the s stem, premature firing of a shot cannot e effected by stray orleakage currents. Furthermore, because the current generated by thegenerator element is of high voltage and low amperage, such currcntsuffers but small loss in its transmission through the long leadconductors, and there is little tendency of loss of it due to poorjoints in conductors. Accordingly, the system has the additionaladvantage of minimizing shot failures. Furthermore, the small lead wiresmake for ease, speed and economy of connecting up a single shot,multiple shots in parallel, series or parallel series.

According to the provisions of the patent statutes, I have explained theprinciple and operation of my invention and have described anddiagrammatically illustrated two embodiments of it. However, I desire tohave it understood that, within the scope of the appended claims, theinvention may be practiced by other apparatus than that particularlyshown and described.

I claim as my invention:

1. A shot firing system, comprising a generator for generating analternating electric current of high volt-age and low amperage and afrequency much greater than that of commercial currents, a transformerfor transforming said generated current into one of low voltage and highamperage, and lead conductors closing a circuit between said generatorand transformer whereby the transformer may be placed close to thecharge to be fired and the generator at a safe distance from it.

2. A shot firing system, comprising a gen-' erator for generating analternating electric current of high voltage and low amperage and of apredetermined frequency much greater than that of commercial currents, atransformer tuned to transform said generated current to one of lowvoltage and high amperage, and long lead conductors closing a circuitbetween said generator and transformer whereby the transformer maybeplaced close to a charge to be fired and the generator at a safedistance from it, and whereby such commercial currents as may gainaccess to said conductor are rendered ineffective for firing a shot.

3. A shot firing system, comprising a generator for generating analternating electric current of high voltage and low amperage and afrequency much greater than that of commercial currents, a transformerfor transforming said generated current into one of low voltage and highamperage, and lead conductors closing a circuit between said generatorand transformer whereby the transformer may be placed close to thecharge to be fired and the generator at a safe distance from it; andprotectors in said circuit adjacent to said generator and to the primaryof said transformer to prevent their injury by stray currents of largemagnitude.

4. A shot firing system, comprising a generator for generating analternating electric current of high voltage and low amperage and afrequency much greater than that of commercial currents, a transformerfor transforming said generated current into one of low voltage and highamperage, and lead conductors closing a circuit between said generatorand transformer whereby the transformer may be placed close to thecharge to be fired and thegenerator at a safe distance from it; andfuses in said circuit adjacent to said generator and to the primary ofsaid transformer to prevent their injury by stray currents of largemagnitude.

5. A shot firing system, comprising a current generating unit consistingof a battery, a battery circuit, means for interrupting the flow ofcurrent through said circuit at a rate much higher than the frequency ofcommercial alternating currents, and a transformer having a primary insaid circuitfor inducing in its secondary a high tion of said batterycircuit; a second transformer whereby the SGCOHddIMDGd transformer tunedto transform said generated former may be placed close to a charge toalternating current to one of low voltage be fired and said generatingunit at a safe 10 and high amperage, and long lead conducdistance fromit. Y

5 tors closing a. circuit between said second In testimony whereof, Isign my name.

secondary of said first-named transformer and h Primary of saidsecond-named trans- JOHN J. JAKOSKY.

